The present invention relates to a method of relining a refractory lined vessel which is used to carry out a molten-based direct smelting process that produces molten metal under conditions requiring molten bath temperatures of at least 1000xc2x0 C.
The present invention relates particularly, although by no means exclusively, to a method of relining a refractory lined vessel which is used to carry out the HIsmelt molten bath-based direct smelting process.
The present invention also relates to a refractory lined vessel which is constructed having regard to the relining method of the present invention.
The term xe2x80x9cdirect smelting processxe2x80x9d is understood to mean a process that produces a molten metal directly from a metalliferous feed material, such as iron ore and partly reduced iron ore.
One known group of direct smelting processes is based on the use of electric furnaces as the major source of energy for the smelting reactions.
Another known direct smelting process, which is generally referred to as the Romelt process, is based on the use of a large volume, highly agitated molten slag bath as the medium for smelting top-charged metal oxides to metal and for post-combusting gaseous reaction products and transferring the heat as required to continue smelting metal oxides.
Another known group of direct smelting processes that are slag based is generally described as xe2x80x9cdeepxe2x80x9d slag processes. These processes, such as DIOS and AISI processes, are based on forming a deep layer of molten slag with a number of regions, including: an upper region for post-combustion reaction gases with injected oxygen; a lower region for smelting metal oxides to metal; and an intermediate region which separates the upper and lower regions.
The HIsmelt direct smelting process relies on a molten metal layer as a reaction medium and includes the steps of:
(a) forming a bath of molten metal and slag in a vessel;
(b) injecting into the bath:
(i) metalliferous feed material, typically, metal oxides; and
(ii) a solid carbonaceous material, typically coal, which acts as a reductant of the metalliferous feed material and as a source of energy; and
(c) smelting the metalliferous feed material to metal in the metal layer.
The HIsmelt process also includes post-combusting reaction gases, such as carbon monoxide and hydrogen, released from the bath, in the space above the bath with oxygen-containing gas and transferring the heat generated by post-combustion to the bath to contribute to the thermal energy required to smelt the metalliferous feed material.
The HIsmelt process also includes forming a transition zone above the nominal quiescent surface of the bath in which there is a favourable mass of ascending and thereafter descending droplets or splashes or streams of molten material which provide an effective medium to transfer to the bath the thermal energy generated by post-combusting reaction gases above the bath.
A preferred form of the HIsmelt process is described in International application PCT/AU99/00538 in the name of the applicant and the disclosure in this International application is incorporated herein by cross-reference.
There is a range of known vessels that has been developed to undertake the above-described and other known molten bath-based direct smelting processes.
By way of example, a vessel for carrying out the HIsmelt process is described in International application PCT/AU99/00537 in the name of the applicant. The disclosure in this International application is incorporated herein by cross-reference.
One factor that is relevant to the economics of direct smelting processes is the amount of time that is required to reline vessels that are used to carry out the processes. During this time molten metal production must cease.
In the case of the Hismelt process, the applicant expects that a partial reline would be required annually and a full reline would be required every two years. The term xe2x80x9cpartial relinexe2x80x9d of a vessel is understood to mean a reline which replaces refractories in the side wall of the vessel and optionally some hearth repairs/upper vessel repairs to patch these sections of the vessel.
The term xe2x80x9cfull relinexe2x80x9d of a vessel is understood to mean a reline which replaces the side wall refractories and also replaces the refractories in the vessel floor and replaces the water cooled panels in the side wall and top wall.
According to the present invention there is provided a method of relining a vessel that is used to carry out a direct smelting process that produces molten metal under conditions requiring molten bath temperatures of at least 1000xc2x0 C., which vessel has a floor that is refractory lined, a side wall that is at least partially refractory lined, and a top wall, and at least two access openings to the interior of the vessel, whereby after shutting down operation of the direct smelting process, the relining method includes the steps of cooling down the vessel, gaining access to the interior of the vessel via the access openings, relining the vessel, and re-starting operation of the process in a period of time of 21 or less days.
Preferably the shutdown period is 20 or less days. More preferably the shutdown period is 18 or less days.
More preferably the shutdown period is 15 or less days.
Preferably there is at least one access opening in the vessel side wall in a hearth region of the vessel and at least one access opening in an upper section of the vessel.
More preferably, there are 2 side wall access openings in the hearth region of the vessel and at least one access opening in the upper section of the vessel.
It is preferred that the side wall access openings be diametrically opposed.
It is preferred that the side wall access openings be in the form of closable doors in the side wall.
Preferably there is a further access opening in the floor of the vessel.
Preferably the vessel includes at least one solids injection lance extending through the side wall and at least one lance for injecting oxygen-containing gas into an upper region of the vessel.
Preferably the side wall of the vessel includes water-cooled panels.
Preferably the top wall of the vessel incudes water-cooled panels.
Preferably the vessel includes a forehearth.
With the above-described construction of the vessel, preferably the step of cooling down the vessel is completed in 24 or less hours.
Preferably the cooling down step cools down the vessel by forced convection cooling or by quench cooling. Without taking such specific steps the cooling down period needed before personnel enter the vessel to commence a conventional reline can take days, with the overall reline likely to take well over a month.
In addition, with this vessel preferably the step of gaining access to the interior of the vessel via the access openings is completed within 30 or less hours in the case of a partial reline of the vessel and 54 or less hours in the case of a full vessel reline.
Typically, in both a partial reline and a full reline of the vessel this step includes isolating the vessel from sources of feed materials, removing lances/tuyeres, and opening the access openings.
Further, with this vessel preferably the step of relining the vessel is completed in 370 or less hours in the case of the partial reline of the vessel and 492 or less hours in the case of the full vessel reline.
Typically, the step of relining the vessel in the partial reline includes the steps of removing the existing refractory lining, installing a safety lining on the side wall, installing a hot face lining on the safety lining, installing a slag zone lining on the safety lining, installing lances/tuyeres, and connecting the vessel to feed materials sources.
Preferably the safety lining includes an outer permanent lining and an inner replaceable refractory brick lining, and the step of installing the safety lining includes patching the permanent lining and laying a new replaceable brick lining.
Preferably the hot face lining and the slag zone lining are formed from refractory bricks.
Typically, the step of relining the vessel in the full reline includes the above-described partial reline steps and also includes the steps of replacing water cooled panels in the side and top walls, removing and replacing the forehearth, and installing a refractory floor.
Preferably the step of replacing the water cooled panels in the top wall includes removing the top wall, replacing the water cooled panels in the top wall, and thereafter repositioning the top wall on the vessel.
Preferably the step of relining the vessel in the full reline includes bricking the forehearth connection between the forehearth and the vessel and using the brickwork of the forehearth connection that extends into the vessel as a key for the brickwork for the replaceable safety lining and the hot face lining.
Preferably the step of installing the refractory floor includes laying one or more courses of precast refractory blocks as a sub-floor and laying a top course of refractory bricks on the sub-floor.
Further with this vessel preferably the step of re-starting operation of the direct smelting process after relining is completed in 96 or less hours.
Preferably the step of relining the vessel includes positioning a safety platform above a hearth region of the vessel and thereby dividing the vessel into two work zones, one above the safety platform and the other below the safety platform, so that relining work can be carried out simultaneously in both zones.
Preferably the step of relining the vessel includes positioning on the platform an assembly that can support and raise and lower water cooled panels and using the assembly as required to remove water cooled panels from the side wall or the roof and positioning replacement water cooled panels on the side wall or the roof.
According to the present invention there is also provided a vessel for carrying out a direct smelting process, which vessel includes: a base which defines a vessel floor, a side wall, and a top wall, an off-gas duct, at least one solids injection lance/tuyere extending through the side wall, at least one lance for injecting an oxygen-containing gas into an upper region of the vessel, a refractory lining at least in a hearth region of the vessel which contains molten material during operation of the process, and at least one access opening in the side wall in the hearth region.
Preferably the vessel includes 2 access openings in the side wall in the hearth region.
Preferably the vessel includes an access opening in the vessel floor.
Preferably the floor access opening is a removable plug.
Preferably the vessel includes one or more courses of precast refractory blocks which form a sub-floor and a top course of refractory bricks laid on the sub-floor.
Preferably the top wall is removable from the vessel.
Preferably the vessel includes a forehearth for discharging molten metal from the vessel.
Preferably the forehearth can be disconnected from the vessel.